Reactive pasty two- or multi-component systems must be stored separately after their production and until their application in order to prevent premature, inadvertent reactions of the components. Cartridge systems for the application of pasty two- or multi-component systems have been known for decades. The following documents are cited for exemplary purposes, CH 669 164 A5, EP 0 607 102 A1, EP 0 236 129 A2, DE 3 440 893 A1, U.S. Pat. No. 4,690,306 A, US 2009/062808 A1, EP 0 787 535 A1, WO 2006/005 206 A1, EP 0 693 437 A1, EP 0 294 672 A, EP 0 261 466 A1, and EP 2 008 707 A1. After the cartridges are filled with reactive pastes, the cartridges need to remain safely closed until their application. The pasty two- or multi-component systems are mixed right before their application, usually through the use of static mixers. In this context, the following documents are cited for exemplary purposes, GB 1,188,516 A, U.S. Pat. No. 2,125,245 A, U.S. Pat. No. 5,968,018 A, U.S. Pat. No. 4,068,830 A, US 2003/179648 A1, EP 0 664 153 A1, and EP 0 289 882 A1. In this context, mobile plungers seal the cartridge floors and are subsequently used to squeeze out the pastes during their application.
A number of solutions has been proposed for closing the cartridge system head of the cartridge system.
One simple, but very effective, principle is to close the cartridge head with a closure that can be rotated (EP 0 431 347 A1, DE 2 017 292 A1, U.S. Pat. No. 3,215,298 A). The closure is unscrewed prior to the application. Subsequently, a dispensing tube is screwed into a thread on the cartridge head or fixed through a peg system that simulates a thread. This is disadvantageous in that the user needs to perform rotational motions twice until the paste material can be expelled. Moreover, the closure may be screwed out and the dispensing tube is attached only later. In the interim between the cartridges being opened and the dispensing tube being inserted, ingredients of the pastes may evaporate, especially if the pastes contain volatile substances.
The closure that is in very common use currently in the adhesives and sealant industry is based on the wall material of the cartridge being provided to be very thin at the cartridge head such that said wall can be perforated easily. During perforation, particles become detached from the wall and can thus enter the pasty material.
A further cartridge system is based on packaging pasty multi-component systems in tubular bags (WO 2010/006455 A1). This involves inserting the sealed tubular bags into cartridges. Tubular bags are advantageous in that they are suitable for packaging pastes that contain volatile ingredients. Tubular bags made of compound materials, such as aluminium compound bags, are particularly well-suited for this purpose. The tubular bags are opened by blades that rotate along when the dispensing tube is being screwed in. The bags are cut open in the course of the rotational motion of the blades and openings in the cartridges for dispensing the content are thus provided. The pasty bag content is subsequently squeezed through these openings in the cartridges in the direction of the static mixer.
In this context, it is disadvantageous that packaging pasty materials in tubular bags and, in addition, in cartridges is quite expensive and reserved for special applications only. Moreover, it is a problem in many applications, especially in the field of medicine, that parts of the cut tubular bags may become detached and thus may enter into the pasty components and thus contaminate the mixing ware.
Currently, pasty components from cartridge systems of adhesives and sealants are usually squeezed out through mechanical squeezing devices that are operated through hand motions of the user. This is disadvantageous in that the user needs to make a strong physical effort, in particular if large volumes are to be squeezed out. Besides, compressed air-operated applicator devices are customary, in particular in industrial applications of cartridge systems, in which pasty substances need to be applied continuously over a relatively short period of time. Said devices are connected to compressors through compressed air hoses or compressed air lines.
Another option is to squeeze out cartridges through compressed gases that are stored in gas cartridges that are situated in applicator devices. Said systems have generally been known for decades.
U.S. Pat. No. 2,818,899 proposes a sealant gun that contains a gas cartridge in its handle. Once the cartridge is opened, the compressed gas of the gas cartridge presses a plunger within the cartridge in the direction of the cartridge head. The flow of the pasty mass is controlled by a central rod that extends through the cartridge and can close the outlet opening of the cartridge.
U.S. Pat. No. 3,938,709 (1976) describes a dispensing device in which gas pressure is used to squeeze out a tube that is situated inside the hollow gun body. In this context, the gas flow is attained through a simple pin valve having a spring that can be actuated through a manual lever. A device for release of the gas was not provided. This means that the gun continues to squeeze the material due to the existing residual pressure although the gas feed is interrupted.
EP 0 169 533 A2 (1985) discloses an injection device for viscous substances. In this device, the squeezing process does not continue after the supply of compressed gas is interrupted, because an injection control valve that interrupts the flow of viscous substance is situated at the outlet opening. What is interesting in this context is that the valve of the trigger grip can be used to control both the supply of gas and the exit of the viscous substance. The injection control valve closes when there is no application of compressed gas.
A similar system is described in U.S. Pat. No. 4,925,061. However, in this system the injection control valve is actuated through a rod that is connected to the trigger grip.
A gun for squeezing out bone cement is disclosed in EP 1 118 313 A1. Propulsion is effected through a gas cartridge in this case also. What is essential is that this very complex system includes a rod that serves the purpose to expel the residual amount of cement contained in the dispensing tube. This elegant technical solution is very well-suited for conventional polymethylmethacrylate bone cements. However, said gun cannot be used for cartridge systems for mixing multiple components through a static mixer. Moreover, the manufacture of said gun is very elaborate.
US 2004/0074927 A1 describes an applicator gun which discloses essentially the same features as U.S. Pat. No. 4,925,061.
Printed publications US 2005/0230433 A1, US 2005/0247740 A1, and U.S. Pat. No. 6,935,541 B1 propose basically the same technical solution that is known already from EP 0 169 533 A2.
WO 2008/109439 A1 discloses a compressed gas-operated dispensing device that uses a hydraulic medium onto which the compressed gas exerts pressure.
It should be noted that the dispensing devices known to date, which are propelled by gas cartridges and have a complex mechanical structure, are suitable for manufacture as disposable articles only to a limited extent or not at all. Especially the valves proposed thus far are very expensive and thus make the use of the dispensing devices as disposable articles questionable. Moreover, the proposed technical solutions are difficult to implement in the form of plastic injection moulding parts.
Polymethylmethacrylate bone cements have been in use in medicine for decades for permanent mechanical fixation of total joint endoprostheses. They are based on powder-liquid systems. Recently, polymethylmethacrylate bone cements that are based on the use of cement pastes have been proposed as well (DE 10 2007 050 762 A1, DE 10 2008 030 312 A1, DE 10 2007 052 116 A1). Thus far, no suitable cartridge systems have been proposed for said cements.
With regard to the application of bone cements for fixation of total joint endoprostheses, it is always necessary to take into consideration that the OR staff is under time pressure during these surgeries. Therefore, as a matter of principle, cartridge systems for medical applications involving the application of paste-like polymethylmethacrylate bone cements should be designed such that they are largely resistant to user errors and can be operated rapidly and safely even in stressful situations.
The methylmethacrylate monomer is an essential ingredient of paste-like polymethylmethacrylate bone cements. Said monomer evaporates readily and has a relatively high vapour pressure at room temperature. For this reason, it is essential to note with regard to the use of methylmethacrylate-containing pastes that the cartridge plungers in the cartridges may be moved and may be expelled from the cartridges in the extreme case by the evaporating methylmethacrylate upon exposure to a vacuum, such as during the de-gassing as part of ethylene oxide sterilisation.